The present invention relates to a high-frequency circuit cooling apparatus for cooling high-frequency circuits which operate at low temperatures, and high-frequency circuits which heat in operation, etc.
As high-frequency circuits which operate at low temperatures of below 100 K including 100 K, filters using oxide high temperature superconductors, such as YBCO, etc., low noise amplifiers comprising GaAs-based semiconductors, and others are known.
Among the high-frequency circuits which operate at such low temperatures, circuits treating higher power, such as superconducting transmission filters, etc., are required to have the interiors of the packages to be sufficiently cooled for being applied to mobile communication stations using the transmission band of frequencies of some GHz including some GHz. They are required to be mounted on cooling apparatuses which facilitate high-frequency circuit being replaced for maintenance. Furthermore, heating due to the quench of the superconductors is required to be quickly removed, and the thermal conduction is required to be changed in tests.
When a superconductor is cooled to a required temperature and has the superconducting state, heating of the superconductor at frequencies of about some GHz is lower by 1-2 placements or more than the normal conductor. On the other hand, high-frequency circuits using superconductors as the circuit conductors include, in many cases, members, such as electrodes, etc., formed of normal conductors. Heat is often conducted from the outside through cables, etc., and heat due to flow of current often inflows from connectors, cables, etc. Accordingly, the high-frequency circuits using superconductors as the circuit conductors are required to be sufficiently cooled.
The high-frequency circuits have been cooled by the following methods.
For example, the package container accommodating a high-frequency circuit is heat-contacted with the cold head of a freezer to cool the high-frequency circuit by thermal conduction.
A metal container to be filled with helium gas is provided with the cold head of a freezer, and a package container accommodating a high-frequency circuit is placed in the metal container. Further, the cold head and metal container is placed in a vacuum container. Helium gas is fed from outside of the vacuum container. In this state, the cold head cools the package container accommodating the high-frequency circuit.
A package container accommodating a high-frequency circuit is immersed in liquid nitrogen and liquid helium to cool the high-frequency circuit.
However, the conventional cooling method for high-frequency circuits have found it difficult to make sufficiently cooling the high-frequency circuits compatible with facilitating the replacement and maintenance of the high-frequency circuits.
Following references disclose the background art of the present invention.
[Patent Reference 1]
Japanese published unexamined patent application No. 2000-307306
[Patent Reference 2]
Japanese published unexamined patent application No. Hei 04-263768 (1992)
[Patent Reference 3]
Japanese published unexamined patent application No. 2000-294399